Free space optical communication (FSO) has evolved as a substitute to radio frequency communication over the few years. It gives a promising solution to the high-speed point-to-point communication. However, atmospheric absorption, scattering and turbulence cause considerable degradation of the wireless optical communication, which degrades system performance. Another major factor which concerns the system performance is the attenuation of signals due to the aforementioned atmospheric reasons. There are different factors in which the atmospheric turbulence conditions are observed using Gamma Gamma Model. Simulations have been carried out in the OptiSystem 14.0 software to study the impact of different weather conditions (clear, haze and fog) on the performance of the channel. Simulation results show that by implementing Multiple Input Multiple Output (MIMO) techniques for FSO systems, it is possible to reduce the BER for different range and achieve the accurate transmitted data at the receiver side. The performance improvements vis-a-vis, received power levels, bit error rate (BER), Q-factor and link distance range have been demonstrated in the presence of atmospheric turbulence conditions like haze, fog, clear sky etc. © 2019 Journal of Communications.